JPH0648633B2 - Induction heating cooker - Google Patents

Description

TECHNICAL FIELD The present invention relates to an induction heating cooker used in a general household.

2. Description of the Related Art A conventional induction heating cooker of this type is shown in FIG. In FIG. 2, 1 is an AC power source, 2 is a bridge-type rectifier, 3
Is an inverter for generating high frequency power, which includes a heating coil 4, a resonance capacitor 5, a transistor 6, a diode 7, a choke coil 8 for stabilizing the output of the rectifier 2 against high frequencies, and a capacitor. It is composed of 9 and 9. Reference numeral 10 is a control circuit that controls the transistor 6, 11 is a power supply circuit that supplies power to the control circuit 10, and the power supply circuit 11 includes a smoothing capacitor 12, a resistor 13, and a switching transistor 14.
, Reactor 15 and flywheel diode 16
When a reference voltage source 17 for generating a reference voltages _{V 1,} by comparing the power supply voltage Vcc of the reference voltages _{V 1} and the control circuit 10 Vcc <the switching transistor 1 when _{V 1}
A comparator 18 for stabilizing Vcc by turning on 4 and turning off when Vcc> V ₁ , and drive resistors 19 and 20 of the switching transistor 14.
It consists of and. Reference numeral 21 denotes the smoothing capacitor 1 during the phase period in which the absolute value of the voltage of the AC power source 1 is near 0.
A diode for preventing the electric charge of 2 from being discharged to the inverter 3, and a switch 22 for turning on / off the AC power supply 1.

However, in the above-described conventional configuration, when the switch 22 is turned on, resonance occurs between the choke coil 8 and the capacitor 9 and a significantly high voltage is generated in the smoothing capacitor 12, so that a switching transistor is generated. 14 and flywheel diode 16 breakdown voltage, or comparator 18
There is a problem in that the withstand voltage of the output terminal must be extremely high, and the cost is very high.

In the conventional induction heating cooker shown in FIGS. 3 and 2, after turning off the switch 22 for a sufficient time,
The voltage V of the capacitor 9 when the switch 22 is turned on at the phase where the instantaneous value of the voltage of the AC power supply 1 is maximized.
₉ , the current I _{9 of the} capacitor 9, the output voltage V ₂ of the rectifier _2, and the voltage V ₁₂ of the smoothing capacitor 12 are shown. In this case, the transistor 6 is off. As is clear from FIG. 3, it is understood that a voltage twice the maximum value V _m of the instantaneous value of the AC power supply 1 is applied to the smoothing capacitor 12. In addition, L is the inductance of the choke coil 8 and C is the capacitance of the capacitor 9.

The present invention solves the above-mentioned conventional problems, and lowers the withstand voltage of the switching transistor and the flywheel diode and the withstand voltage of the output terminal of the comparator by preventing the high voltage from being generated in the smoothing capacitor, and the low-cost induction heating cooker. The purpose is to provide.

Means for Solving the Problems In order to solve the above problems, an induction heating cooker according to the present invention includes a first rectifier composed of a bridge diode and a high-frequency current connected to an output terminal of the first rectifier. A generating inverter, a control circuit for controlling the inverter, a power supply circuit for supplying a current to the control circuit, and at least one input terminal of the first rectifier and an input terminal of the power supply circuit. A second rectifier including a diode, wherein one input terminal of the power supply circuit is connected to one output terminal of the first rectifier, and the other input terminal is one output terminal of the second rectifier. Induction heating cooker connected to.

Operation According to the above configuration, it is possible to prevent a high voltage from being generated at the input terminal of the power supply circuit when the power is turned on by the second rectifier, so that it is possible to reduce the breakdown voltage of the element that configures the power supply circuit.

Embodiment One embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a circuit diagram of an induction heating cooker according to an embodiment of the present invention, in which 31 is an AC power source, 32 is a bridge-type first rectifier, and 33 is an inverter that generates high-frequency power. It is composed of a heating coil 34, a resonance capacitor 35, a transistor 36, a diode 37, a choke coil 38 for stabilizing the output of the first rectifier 32 against high frequencies, and a capacitor 39. 40 is a control circuit for controlling the transistor 36,
41 is a power supply circuit for supplying power to the control circuit 40,
The power supply circuit 41 includes a smoothing capacitor 42 and a resistor 43.
, Switching transistor 44, and reactor 45
On the, a flywheel diode 46, a reference voltage source 47 for generating a reference voltages _{V 1,} by comparing the power supply voltage Vcc of the reference voltages _{V 1} and the control circuit 40 Vcc <a switching transistor 44 when _{V 1} And Vcc>
A comparator 48 for stabilizing Vcc by turning it off at V ₁ , and the switching transistor 44.
Drive resistors 49 and 50 of the above. 51 is a switch for turning on / off the AC power supply 31, 52 is a diode 53, 54,
The respective anodes of 54 are second rectifiers connected to both input terminals of the first rectifier 32 and the cathodes commonly connected to serve as output terminals.

The operation of the above configuration will be described below. AC power supply 31
When the switch 51 is turned on in a phase in which the instantaneous value of the voltage is maximized, the voltage and current of the capacitor 39 and the output voltage of the first rectifier 32 are the same as those in the conventional example shown in FIG.
It becomes like (a) (b) (c). However, in the present embodiment, even if a high voltage is generated at the output terminal of the first rectifier 32, it is blocked by the second rectifier 53, so the output voltage of the first rectifier 32 is input to the input terminal of the power supply circuit 41. Will not be added.

As described above, in the present embodiment, when the switch 51 is turned on, a high voltage is not generated at the input terminal of the power supply circuit 41, so that the withstand voltage of the switching transistor 44 and the flywheel diode 46 and the withstand voltage of the output terminal of the converter 48 are reduced. Can be lowered.

As described above, according to the present invention, the second rectifier can prevent a constant voltage from being generated at the input terminal of the power supply circuit when the power is turned on. Therefore, the withstand voltage of the elements forming the power supply circuit can be reduced. Since it can be lowered, the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an induction heating cooker according to an embodiment of the present invention, FIG. 2 is a circuit diagram of a conventional induction heating cooker, and FIG. 3 is a signal waveform of each part when the power of the induction heating cooker is turned on. It is a figure. 32 ... First rectifier, 33 ... Inverter, 40 ...
Control circuit, 41 ... Power supply circuit, 52 ... Second rectifier,
53, 54 ... Diode

Claims (2)

[Claims] 1. A first rectifier composed of a bridge diode, an inverter connected to an output terminal of the first rectifier for generating a high frequency current, a control circuit for controlling the inverter, and a current for the control circuit. A power supply circuit for supplying power; and a second rectifier including a diode connected between at least one input terminal of the first rectifier and an input terminal of the power supply circuit, wherein one input terminal of the power supply circuit is provided. An induction heating cooker connected to one output terminal of the first rectifier and having the other input terminal connected to one output terminal of the second rectifier. 2. The second rectifier is composed of two diodes whose anodes or cathodes are connected to each other, and the connection point of the series circuit of the two diodes is an output and both ends are inputs. The induction heating cooker according to item 1.